1. Field of the Invention
In air-compressing internal combustion engines, fuel injection systems are increasingly being used that for instance include injectors that are supplied with fuel via a high-pressure collection chamber (common rail), or injectors with pressure boosters or unit fuel injector systems. The fuel injection systems listed predominantly include 2/2-way valves, which as a rule are not in a state of pressure equilibrium.
2. Prior Art
European Patent Disclosure EP 0 987 431 A2 has a fuel injector for internal combustion engines as its subject. The fuel injector includes a nozzle needle, which is vertically movably received inside a bore in the injector housing. One face of the nozzle needle partly defines a control chamber, which communicates with a supply line via a restriction. By means of a control valve, the communication between the control chamber and a low-pressure region is controlled. There is also a valve for communication between the supply line and the low-pressure region. This valve and the control valve each include armature elements, which are actuatable by means of an electromagnetic actuator that is common to both valves.
European Patent Disclosure EP 1 081 373 A2 likewise has a fuel injector as its subject. It is used in an arrangement that includes a fuel pump, a pump chamber, and a first valve; this first valve controls the communication between the pump chamber and a low-pressure region. The injector includes a nozzle needle, which can be brought into interaction with a needle seat. A control chamber is disposed such that the fluid pressure prevailing in it presses the nozzle needle into its needle seat. The fluid pressure inside the control chamber is controlled by means of a control valve. The control valve in turn is controlled via an actuating assembly in such a way that when the actuating assembly is not activated, the control valve opens a fluid communication between the control chamber and the low-pressure region.
In the version of EP 1 081 373 A2, 2/2-way valves are used on the outlet side relative to a control chamber. The use of such 2/2-way valves on the inlet side of a control chamber, which acts upon a control piston that indirectly actuates the nozzle needle, is unfavorable because of the high actuation forces required.